The invention relates to an automatic coffeemaker comprising, in a housing, a fixed body which comprises a cylinder closed, on the one hand, by a cover and, on the other hand, by a ferrule traversed by a rotating shaft connected to motor means, and in which are provided openings, an opening for passage of the grind adapted for the introduction of a quantity of ground coffee, a feed opening for liquid adapted to introduce a quantity of hot water from a water heater, an outlet passage for the infusion, and an opening for ejection of the grounds.
The invention concerns more particularly a coffeemaker of this type in which said cylinder is so arranged as to enclose a cylindrical infusion chamber delimited at its ends, on the one hand, by a cover and, on the other hand, by the front surface of a piston which is slidably mounted in the cylinder thanks to translatory drive means fixed for rotation with said shaft, and which can occupy at least two positions, either a rest position in which the piston is retracted from the opening of the passage for the grind, permitting the flow of said grind into the chamber, or a packing position in which the opening of the passage for the grind being closed, the piston packs the grind below the ejection opening against the cover.
In known machines of this type, the ground coffee is introduced into the infusion chamber which is then sealed. The piston packs the grind. Hot water is then passed through the grind, then when the infusion is produced, it is removed by the infusion outlet opening, while the grounds are ejected. To perform this cycle, recourse is had to complicated and costly mechanisms of little reliability at this time.
Moreover, these machines permit producing only an infusion of the "espresso" type, the volume of the infusion chamber being constant at the time of infusion, and the pressure exerted by the piston being also continuously constant.